Conventionally, an image display device disclosed in Patent Document 1 is known as one example of an image display device. The image display device disclosed in Patent Document 1 is provided with an image display element that displays an image, a light beam refraction unit formed in a flat plate shape arranged adjacent to an image display surface of the image display element so as to refract a main light beam in a light beam emitted by the image display element such that the main light beam is diffused outward, and an eyepiece optical system that guides the light beam passed through the light beam refraction unit to an eye ball of an observer and displays an enlarged image of the image displayed by the image display element.